Canola oil has the lowest level of saturated fatty acids of all vegetable oils. As consumers become more aware of the health impact of lipid nutrition, consumption of canola oil in the U.S. has increased. However, generic canola oil has limited use in deep frying operations, an important segment of the food processing industry, due to its instability. Canola oil extracted from natural and commercial varieties of rapeseed contains a relatively high (8%-10%) .alpha.-linolenic acid content (C.sub.18:3) (ALA). The oil is unstable and easily oxidized during cooking, which in turn creates off-flavors of the oil and compromises the sensory characteristics of foods cooked in such oils. It also develops unacceptable off odors and rancid flavors during storage.
Hydrogenation can be used to improve performance attributes by lowering the amount of linoleic and .alpha.-linolenic acids in the oil. In this process the oil increases in saturated and trans fatty acids, both undesirable when considering health implications. Blending of oil can also be used to reduce the .alpha.-linolenic acid content and improve the performance attributes. Blending canola oil with other vegetable oils such as cottonseed will increase the saturated fatty acids content of the oil but decreases the healthy attributes of canola oil.
.alpha.-Linolenic acid has been reported to oxidize faster than other fatty acids. Linoleic and .alpha.-linolenic acids have been suggested as precursors to undesirable odor and flavor development in foods. To improve the functionality of canola oil, the University of Manitoba developed the canola variety "Stellar" which has reduced .alpha.-linolenic acid (Scarth et al., Can. J. Plant Sci., 68:509-511 (1988)). The low .alpha.-linolenic acid oil was reduced in odor when heated in air, but still remained unacceptable to the sensory panel in flavor evaluations (Eskin et al., J. Am. Oil Chem. Soc. 66:1081-1084 (1989)). The oxidative stability of Stellar oil increased by 17.5% over the commercial variety Westar as measured by Active Oxygen Method (AOM) hours. (Can. J. Plant Sci. (1988) Vol. 68, pp. 509-511).
European Patent Application, EP 0 323 753 A1 describes a canola oil having an enhanced oleic acid content with increased heat stability in combination with other traits. The application further describes a frying oil with reduced .alpha.-linolenic acid which imparts increased oxidative stability. No flavor and performance testing with the described oil was reported.
Data which shows that oxidative stability is not solely related to fatty acid composition (described below) indicates that increased stability cannot be inferred from fatty acid composition. The amount of .alpha.-linolenic acid in the oil is only one factor which controls oxidative stability and flavor stability. Thus a canola oil which has improved stability in its flavor and performance attributes for use in food operations is needed. The present invention provides such an oil.